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This paper presents results of thin film contact resistance with dissimilar materials. The model assumes arbitrary resistivity ratios and aspect ratios between contact members, for both Cartesian and cylindrical geometries. It is found that the contact resistance is insensitive to the resistivity ratio for a/h < 1, but is rather sensitive to the resistivity ratio for a/h > 1 where a is the constriction size and h is film thickness. Various limiting cases are studied and validated with known results. Accurate analytical scaling laws are constructed for the contact resistance over a large range of aspect ratios and resistivity ratios. Typically the minimum contact resistance is realized with a/h ∼ 1, for both Cartesian and cylindrical cases. Electric field patterns are presented, showing the crowding of the field lines in the contact region. [ABSTRACT FROM AUTHOR]

The lumped circuit elements representing electrical contact of a single and multiple contact points are constructed. The local electrical contact is assumed to be in the form of a cylindrical constriction (connecting bridge) of radius a and axial length 2h, made of the same material as the main conducting current channel of radius b. The resistance, capacitance, and the inductance of the electrical contact are given in terms of a, b, and h, from which the rf properties of electrical contact are obtained. For the case of conducting surfaces with a single connecting bridge with dimension in micron size, the resulting resonant frequency is found to be in the terahertz regime. A statistical analysis on a distribution of these dimensions follows. It is found that for multiple contact points, the quality factor (Q) and the resonance frequency (ω0) are roughly independent of N, whereas the characteristic impedance (Zc) is proportional to 1/N, where N represents the number of contact points. The implications of these findings are discussed. [ABSTRACT FROM AUTHOR]

The radio-frequency (rf) power absorption due to a small hemispherical protrusion on a resonant cavity’s surface is computed analytically. This protrusion may assume arbitrary values of permittivity, permeability, and conductivity so that it may represent a foreign object. Under the assumption that the protrusion radius, a, is small compared with the rf wavelength, the power dissipated in the protrusion by the rf electric field and by the rf magnetic field are calculated explicitly. It is found that, in general, the heating by the rf magnetic field is dominant when δ/a<1, even for nonmagnetic materials, where δ is the skin depth associated with the protrusion material. The field enhancement factors for both the rf electric field and the rf magnetic field on the protrusion are also calculated analytically. They are found to decrease as δ/a increases. They are spot checked against the MAXWELL 3D code. These field enhancement factors are also consistent with the published results in the δ=0 limit, in which case the protrusion may represent a small local bump on the surface of a superconducting cavity. [ABSTRACT FROM AUTHOR]

Triple point, defined as the junction of metal, dielectric, and vacuum, is the location where electron emission is favored in the presence of a sufficiently strong electric field. In addition to being an electron source, the triple point is generally regarded as the location where flashover is initiated in high voltage insulation, and as the vulnerable spot from which rf breakdown is triggered. In this paper, we focus on the electric field distribution at a triple point of a general geometry, as well as the electron orbits in its immediate vicinity. We calculate the orbit of the first generation electrons, the seed electrons. It is found that, despite the mathematically divergent electric field at the triple point, significant electron yield most likely results from secondary electron emission when the seed electrons strike the dielectric. The analysis gives the voltage scale in which this electron multiplication may occur. It also provides an explanation on why certain dielectric angles are more favorable to electron generation over others, as observed in previous experiments. [ABSTRACT FROM AUTHOR]

A phase-locking model has been developed from circuit theory to qualitatively explain the various regimes observed in magnetron injection-locking experiments. The experiments utilize two continuous-wave oven magnetrons: one functions as an oscillator and the other as a driver. The model includes both magnetron-specific electronic conductance and frequency-pulling parameter. Both time and frequency domain solutions are developed from the model, allowing investigations into the growth and saturation as well as the frequency response of the output signal. This simplified model recovers qualitatively many of the phase-locking frequency characteristics observed in the experiments. [ABSTRACT FROM AUTHOR]

This paper provides a general theory on the Ohmic dissipation of electromagnetic energy by a spherical particulate that is embedded in a lossless medium. The particulate may possess an arbitrary electrical conductivity, and both the medium and the particulate may assume general values of permittivity and permeability. Under the assumption that the wavelength of the electromagnetic field in the medium is large compared with the particulate size, we provide an accurate account of the degree of Ohmic heating by the radio frequency (rf) electric field and by the rf magnetic field of the electromagnetic field. It is found that, in general, heating by the rf magnetic field is dominant whenever δ

Experiments are reported in which two configurations for ablation-plasma-ion-implantation (APII) are characterized by diagnostics and compared. The first configuration oriented the target parallel to the deposition substrate. This orientation yielded ion-beam-assisted deposition of thin films. A delay (>5 μs) between laser and high voltage was necessary for this geometry to avoid arcing between negatively biased substrate and target. The second experimental configuration oriented the target perpendicular to the deposition substrate, reducing arcing, even for zero/negative delay between the laser and the high voltage pulse. This orientation also reduced neutral atom, ballistic deposition on the substrate resulting in a pure ion implantation mode. Ion density measurements were made by resonant laser diagnostics and Langmuir probes, yielding total ion populations in the range of 10[sup 14]. Implanted ion doses were estimated by electrical diagnostics, and materials analysis, including x-ray energy dispersive spectroscopy and x-ray photoelectron spectroscopy, yielding implanted doses in the range 10[sup 12] ions/cm[sup 2] per pulse. This yields an APII efficiency of order 10% for implantation of laser ablated ions. Scaling of ion dose with voltage agrees well with a theory assuming the Child–Langmuir law and that the ion current at the sheath edge is due to the uncovering of the ions by the movement of the sheath. Thin film analysis showed excellent adhesion with smoother films for an accelerating voltage of -3.2 kV; higher voltages (-7.7 kV) roughened the film. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A general theory on the Ohmic dissipation of electromagnetic energy by a spherical particulate that is embedded in a lossless medium is provided. The particulate may possess an arbitrary electrical conductivity, and both the medium and the particulate may assume general values of permittivity and permeability.

Presents a study which used a repetitively pulsed copper vapor laser to machine an opaque polymer and a transparent polymer. Applications of pulsed and carrier wave laser light from the far ultraviolet to the infrared; Materials and methods; Comparison between thermal versus nonthermal ablative machining; Description of the copper vapor laser light-irradiated surface.

Presents information on a study that characterized the ionization dynamics produced in the KrF excimer laser ablation of iron and a laser-ablation-assisted plasma discharge ion source by a dye-laser-based resonant ultraviolet interferometry diagnostic. Experimental procedures; Results and discussion on the study.

Presents a study on the expansion of the laser ablation plumes produced by KrF excimer laser beam using resonant holographic interferometry and dye-laser-resonance-absorption photography. Introduction to laser ablation; Derivation of equations; Experimental setup.

Presents the results of an experimental program which investigated the cumulative beam breakup instability in electron beam accelerators. Large frequency spread experiments; Small frequency spread experiments; Conclusions.

Provides information on a study that derived dispersion relations to determine the growth rate, wavelength and group velocity of disturbances caused by the beam breakup instability in quadruple and solenoidal electron-beam transport systems. Details on the one-dimensional continuum model for quadruple transport; Information on a two-dimensional continuum model for solenoidal transport; Description of discrete spatial effects; Equations for a periodically pulsed beam.

Presents a study which described detailed experiments on the generation of acoustic waves and enhancement of combustion by electron-beam injection. Examples of methods explored for increasing the burning rate of lean fuel-air mixtures; Illustration of the experimental configuration; Materials used in the construction of the apparatus.